Luminescent enhancement of europium metal-based calcium fluoride nanoparticles using surface modifications: a theoretical and an experimental study of the antenna effect
- WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
- Matteo Fratarcangeli (Creator)
- Institution
- Western Carolina University (WCU )
- Web Site: http://library.wcu.edu/
- Advisor
- Channa De Silva
Abstract: Europium metal-based nanomaterials show promising applications in optical imaging of biological samples, bio-analytical sensing, biomedical assay technologies, and high throughput drug screening. They present unique photophysical properties including monochromatic light emission, long luminescent lifetimes enabling time-resolved measurements, limited photobleaching, large Stokes shifts, and negligible ligand field effects. Ligand design and understanding their electronic properties for enhancing the luminescent quantum efficiency of europium-based probes is extremely important for their potential applications in cellular imaging. Among the europium metal-based nanocrystals, europium-doped calcium fluoride nanoparticles are suitable for cellular imaging due to their high biocompatibility compared to previously studied crystal matrices including NaYF4 and LaF3. However, their luminescent efficiencies should be further improved for cellular imaging. In this work, we report a. computational studies of the electronic properties of europium fluorobenzoate complexes aiming to better understand the electronic structure and the luminescent efficiency for designing highly luminescent imaging probes, b. surface modifications of europium-doped calcium fluoride nanoparticles for enhancing their luminescence, and c. preliminary imaging of nanoparticles using epifluorescent microscopy. Our computational studies revealed that the calculated structural parameters agree well with the experimental values. On average, the calculated metal-ligand bonds are shorter in monohydrate complexes compared to those observed for dihydrate complexes. This could affect the electronic excited states and the luminescent efficiency of the complexes. The optimal ISC and ET were identified as 1.1548 eV and 1.3746 eV, respectively for the Eu3+ fluorobenzoate complexes. The correlation among the experimental luminescent quantum yields and the calculated electronic excited states were analyzed providing insight into designing molecular structures for improving europium-centered luminescence. The synthesis of the europium-doped nanoparticles was successful. The smallest nanoparticles had a diameter of 40 nm. X-ray diffraction studies revealed the cubic face-centered crystal structure of CaF2. Surface modification was confirmed using FT-IR and UV-Vis spectroscopy. The nanoparticles present a ?max at 341 nm and a bright orange emission band at 613 nm. The surface functionalization promoted ligand-to-metal energy transfer process resulting in europium-centered luminescence. The luminescent quantum yield of the nanoparticles depends on the size and surface coating. Nanoparticles with an average size of 470 nm and 160 nm presented a maximum luminescent quantum yield of 11.8% and 23.7%, respectively. Preliminary imaging studies of nanoparticles using epifluorescence microscopy revealed that the nanoparticles are clearly visible under 365 nm excitation and can have potential cellular imaging applications.
Luminescent enhancement of europium metal-based calcium fluoride nanoparticles using surface modifications: a theoretical and an experimental study of the antenna effect
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Created on 4/1/2023
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Additional Information
- Publication
- Thesis
- Language: English
- Date: 2023
- Subjects
- Europium
- Calcium fluoride
- Nanostructured materials
- Luminescence
- Microscopy